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PubMed1992

The genotoxicity of chromium(VI) oxide in the wing spot test of Drosophila melanogaster is over 90% due to mitotic recombination.

Chromium(VI) oxide and chromium(III) chloride were tested in the wing somatic mutation and recombination test (SMART) in Drosophila melanogaster according to standard procedures. The hexavalent compound was highly genotoxic in both chronic and acute treatments whereas the trivalent one was clearly negative. Further analysis of wings carrying an inversion chromosome which eliminates all recombination events showed that over 90% of the spots induced by chromium(VI) oxide are due to mitotic recombination.

Animals↗
PubMed2004

Determining the safety of chromium tripicolinate for addition to foods as a nutrient supplement.

Trivalent chromium is an essential element required for normal carbohydrate, lipid, and protein metabolism in humans and animals. This article describes how one particular form of trivalent chromium, chromium tripicolinate (Chromax), a stable complex of trivalent chromium and picolinic acid, was determined to be safe for use as a nutrient supplement in foods (i.e., nutritional bars and beverages). A safety assessment of a nutrient supplement for use in food requires an evaluation of the safety of the product (Chromax), as well as an evaluation of the safety of the intended dietary ingredient (chromium tripicolinate). In this assessment, the production process, final product specifications, and product analysis results for Chromax were evaluated to determine the safety of the final product. Then, the Estimated Daily Intakes (EDIs) of trivalent chromium and picolinic acid from the proposed use of Chromax were calculated using data from the USDA's most recent Continuing Survey of Food Intakes by Individuals. The EDI for trivalent chromium was compared to the Acceptable Daily Intake (ADI) for this compound derived from animal studies, corroborated with human data, while the EDI for picolinic acid was compared to existing in vivo exposure to this compound that occurs naturally in the body. As long as the EDI of trivalent chromium is less than the ADI for this compound and the EDI of picolinic acid is less than its estimated in vivo exposure, Chromax can be considered safe for its intended use. Employing this approach, it was determined that Chromax is safe, as well as generally recognized as safe (GRAS), for use in nutritional bars and beverages as a nutrient supplement at a maximum use level of 2.4 mg of Chromax per product serving.

Adolescent↗
PubMed1992

Protective effects of thiol compounds on chromate-induced cytotoxicity in HeLa cells.

The effects of several thiol compounds on the cytotoxicity induced by chromate (potassium dichromate) were examined. HeLa cells were incubated in Eagle's minimum essential medium (MEM) with or without the chromate alone, or with both chromate and any one of L-cysteine ethyl ester (LCysEE), L-cysteine methyl ester (LCysME), N-acetyl-L-(+)-cysteine, 2,3-dimercaptosuccinic acid (DMSA), 2, 3-dimercapto-1-propanesulfonic acid (DMPS), or dithiothreitol. After a given period of incubation, the number of viable cells was counted using the trypan blue exclusion test and the chromium content of the cells was estimated by atomic absorption spectrophotometry. The results obtained were as follows. 1) Chromate-induced cytotoxicity evaluated by inhibition of cell growth at 3 days of incubation was diminished by all of the thiol compounds tested when the cells were incubated in MEM with 2.5 to 10.0 microM chromate and 25 to 100 microM thiol compounds. 2) All of the thiol compounds produced a concentration-dependent reduction of chromate when a solution of the thiol compound (12.5 to 100 microM) was mixed with a solution of chromate (10 microM) in distilled water. 3) When cells were incubated in MEM with both 10 microM chromate and 25 to 100 microM thiol compounds, the chromium content of the cells at 6 hr of incubation was decreased in a concentration-dependent manner. 4) When these thiol compounds were added to MEM 1 hr before or after chromate, no or little protective effects of these thiol compounds against chromate-induced cytotoxicity and chromium uptake by the cells were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Division↗
PubMed1991

From contacts and bondings between bone and bioactive glass to bonding of bioactive glass and porcelain to metal alloys, different methods of fracture repair.

Bioactive glass has the ability to bond to bone. In this article the contact between glass and bone is discussed and the development of core alloy for an implant coated with bioactive glass and the oxidation of metal surface in ceramic fusion has been studied. Good bonding of coating materials to core alloys is necessary in dental implants. Using a pull test method we studied the bond strengths between various alloys and some composite materials clinically used to repair fractures of porcelain-veneered dental crowns. An experimental bioglass material was also studied. The bonding of composite materials to metal surfaces etched with hydrofluoric acid was almost as good as the bonding between metal and porcelain, or glass.

Adhesives↗
PubMed1988

Induction of micronuclei in Vicia faba root tips treated with heavy metals (cadmium and chromium) in the presence of NTA.

Soluble metal compounds (CdCl2, K2Cr2O7) significantly increase the frequency of micronucleated cells in Vicia faba root tips with a clear dose-effect relationship. The addition of NTA (nitrilotriacetic acid) does not enhance the induction of micronucleated cells. Conversely, insoluble metal compounds (CdCO3, PbCRO4) significantly enhance the frequency of micronucleated cells only in the presence of NTA. Since some genotoxic metals are diffused in the environment and are often sequestered as insoluble precipitates in water sediments and sludges, the introduction of NTA is likely to increase the risk of environmental pollution because of its ability to solubilize and make those metals reactive.

Acetates↗
PubMed2000

Crack initiation modes in bilayered alumina/porcelain disks as a function of core/veneer thickness ratio and supporting substrate stiffness.

We hypothesize that the fracture resistance of alumina core/porcelain veneer disks increases and that crack initiation shifts from veneer to core as the core/veneer thickness ratio (t(C)/t(V)) increases from 0.5/1.0 to 1.3/0.2, or as the elastic modulus of the supporting substrate (E(S)) to which it is resin-bonded increases from 5.1 to 226 GPa. When supported by a low-modulus substrate, disks with low t(C)/t(V) ratios exhibited cracks in the veneer and within the core, while those with high t(C)/t(V) ratios demonstrated core cracks, but not veneer cracks. None of the disks supported by Ni-Cr alloy (E = 226 GPa) exhibited core cracks. These results support the hypothesis that the crack initiation site shifts as the t(C)/t(V) ratio increases, but the increase in E(S) did not affect the crack initiation site. This study suggests that the t(C)/t(V) ratio is the dominant factor that controls the failure initiation site in bilayered ceramic disks.

Aluminum Oxide↗
PubMedDate not supplied

Effects of chromium(III) on DNA replication in vitro.

A number of metal compounds are important environmental carcinogens; however, the molecular mechanisms of metal-induced genotoxicity are not yet understood. Chromium, for example, is substantially mutagenic in vivo and has been shown to decrease the DNA replication fidelity in vitro. But the mechanism of chromium-induced mutagenesis is unknown and the role of replication fidelity in chromium-induced carcinogenesis is unclear. We have used in vitro DNA replication assays to investigate the effects of chromium ions on DNA polymerase activity preliminary to studying their role in chromium-induced mutagenesis. Biologically active M13mp2 DNA was replicated with purified DNA polymerases in the presence of micromolar amounts of chromium with or without the normal divalent cation, magnesium. Nucleotide incorporation kinetics were determined and sequence specific pausing was analyzed by primer-extension. Our results have demonstrated an unexpected polymerase activation by low (0.5-5.0 microns) concentrations of chromium (III), although higher concentrations of chromium are increasingly inhibitory. The increased incorporation seem at low chromium(III) concentrations is the result of increased enzyme processivity and is not polymerase specific. The possible relationship between processivity and metal-ion mutagenesis is discussed.

Chromium↗
PubMed1998

Use of the enriched stable isotope Cr-50 as a tracer to study the metabolism of chromium (III) in normal and diabetic rats.

The activable enriched stable isotope Cr-50 compound Cr2O3 was used as a tracer to study the metabolism of chromium(III) [CR(III)] intragastrically administered in normal and diabetic rats. The comparison of absorption, distribution, and excretion in organs and tissues of the two groups do not show much alteration, but some differences exist indeed. The contents of 51Cr radioactivity of the diabetic rats appear to be of higher retention than in most studied organisms. The urinary 51Cr excretion of diabetics is significantly higher than that of normal rats. Therefore, a conclusion can be drawn that the insulin-dependent rats generally absorb and excrete more chromium (Cr) than the normal rats.

Absorption↗
PubMed2000

[Syntheses of biologically active natural products using metal-mediated reactions as key reactions].

This review deals with total syntheses of biologically active natural products by the use of metal-mediated coupling reactions as key steps. First, we explored the coupling reactions mediated by samarium (II) diiodide (SmI2), which is a useful versatile one electron reducing reagent. The SmI2-mediated coupling reactions of N,N-dibenzyl-alpha-bromoamide and N,N-bis(p-methoxyphenyl)-alpha-bromoamide with carbonyl compounds gave the corresponding beta-hydroxyamides, respectively. Then, oxidative treatment of compound 6c with ceric (IV) ammonium nitrate (CAN) gave d,l-myrmicacine (7b). Synthesis of pyrrolizidine alkaloid pyrrolam A (8), which causes damage to fertilized eggs at a low concentration, was accomplished via the SmI2-mediated cyclization between a bromoalkyl and ynamide group. Next, (+/-)-oxerine (15), a monoterpene alkaloid, was synthesized starting from 3-bromopyridine. The synthesis of (+/-)-oxerine (15) was also carried out via the SmI2-mediated intramolecular cyclization of gamma-ethynyl bromide (40). Next, we focused on the palladium-catalyzed oxidation of alcohol and tried to expand it to the intermolecular cyclization. As a result, treatment of hydroxy-enamines and hydroxy-amines with a palladium catalyst gave the corresponding pyrroles and indoles in moderate to good yields. Finally, the syntheses of three pyrrolidine alkaloids were described. The chromium (II) chloride-mediated coupling reactions of (R)- and (S)-Garner aldehydes (56 and 57) with allyl bromides proceeded with moderate stereoselectivity to afford the corresponding homoallyl alcohols, which were converted to (2R, 3S)-2-hydroxymethyl-3-hydroxypyrrolidine (61), (2R, 3R, 4R)-3-hydroxy-4-methylproline (66), and the enantiomer (77) of (-)-bulgecinine (78).

Bromine Compounds↗
PubMed1988

Investigations on the quantitative determination of nickel and chromium in human lung tissue. Industrial medical, toxicological, and occupational medical expertise aspects.

Nickel (Ni) and some of its relatively insoluble compounds as well as chromates may be able to induce cancer in the region of the lungs, as well as in the nose and paranasal sinuses after occupational exposure. Latency periods may amount to 20 years and more. The results of recent investigations have shown that these metals cumulate in the lung tissue after inhalation of relatively insoluble chromium and nickel compounds. The quantitative detection of these heavy metals in samples of pulmonary tissue hence permits the amount of past exposure to be estimated. To establish the normal values, samples of pulmonary tissue from 30 normal subjects were investigated for chromium and nickel content. The samples were taken from different segments and lobes of the lungs, taking topographical anatomical criteria into consideration. In addition, 15 persons who had formerly been exposed to nickel and/or chromium (11 nickel refinery workers, of whom 10 had died of lung cancer, 2 stainless steel welders, 1 foundry worker, 1 electrical technician) were also investigated. From the results of 495 tissue samples from the normal group, median chromium concentrations between 130 and 280 ng/g were calculated, with median nickel concentrations of 20-40 ng/g (wet weight). If these values are related to the nickel concentrations measured in refinery workers, values 112-5,860 times higher were found. The concentrations were about 500 times higher than normal for nickel, and about 60 times higher than normal for chromium in the stainless steel welders. For the foundry workers who died of lung cancer, chromium and nickel concentrations in the normal range were calculated, with the exception of the nickel concentrations in the upper and lower lobes of the right lung. The very high nickel concentrations found in the samples of lung tissue from former nickel refinery workers should be regarded as a guideline with regard to the appraisal of the causal relationship between lung cancer and occupational exposure to relatively insoluble nickel compounds. This result is also supported by epidemiological investigations on this subgroup and must thus be considered etiologically conclusive. For the welders, chromium and nickel concentrations were found that were markedly above normal, but as yet there is no epidemiologically reliable verification for the increased occurrence of malignancies in this occupational group.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1988

Antibody-mediated platelet destruction by quinine, quinidine, and their metabolites.

Metabolites of quinine and quinidine, along with the parent compounds, were investigated for their ability to promote complement-mediated platelet destruction when combined with drug-dependent platelet antibodies from five patients with quinine- and quinidine-induced thrombocytopenia. In all, eight metabolites and four closely related structural analogues were studied. These included the desmethyl, 2'-oxo, 10,11-dihydroxy, N-oxide, N'-oxide, and diN,N'-oxide derivatives. When we used the cytotoxic chromium 51 release assay, the parent compounds were typically from 10 to greater than 300 times more effective than the corresponding metabolites and structural analogues in promoting antibody-mediated platelet lysis. Reaction patterns varied significantly among all antibodies and compounds studied, strengthening previous evidence that drug-dependent platelet antibodies are extremely heterogeneous in their reactions with platelets. Although most of the metabolites were much less potent than the parent compounds in promoting antibody-mediated platelet lysis, one quinidine-induced antibody was significantly inhibited in its quinidine-mediated lytic activity by the addition of desmethylquinidine, an essentially nonreactive metabolite with this particular antibody. These findings support the hypothesis that the native structures of quinine and quinidine are sufficient to provoke drug-dependent antibody formation and subsequent platelet destruction independently of their metabolites. They also suggest a possible protective role for some of these metabolites in certain individuals who are susceptible to this allergic drug reaction.

Antibody Formation↗
PubMed1992

Occupational exposure to chromium, copper and arsenic during work with impregnated wood in joinery shops.

CCA-impregnated timber contains copper, chromium and arsenic (CCA), and occupational exposure to wood dust as well as the CCA compounds may occur in work with such timber. Dust from commercially available impregnated wood has been found to contain hexavalent chromium, which is regarded as a carcinogen. Apart from determinations of the total amounts of the CCA compounds, specific determination of hexavalent chromium is therefore essential. Selective methods have been applied for control of the work environment in six joinery shops. The mean exposure to wood dust was found to be below 1 mg m-3. The mean airborne concentration of arsenic around various types of joinery machines was in the range from 0.54 to 3.1 micrograms m-3. No hexavalent chromium was detected in any samples and no increased concentrations of arsenic were found in urine from the workers. The presence of arsenic in the work-room air must be considered for appropriate assessment of the occupational environment in joinery shops.

Air Pollutants, Occupational↗
PubMed2005

Reactions of *NO2 with chromium(III) complexes with histamine and pyridoxamine ligands studied by the stopped-flow technique.

This study demonstrated the direct formation of the nitrogen dioxide (*NO2) radical during the decomposition of 3-morpholinosydnonimine (SIN-1) in biological buffer 4-morpholinoethanosulfone acid solution. Consequently, at approximately pH 4, SIN-1 can be used successfully as a source of *NO2. This conclusion is drawn from a comparison of the reactions of cis-[Cr(C2O4)(L- L)(OH2)2]+, where L-L denotes pyridoxamine (Hpm) or histamine (hm), with the gaseous *NO2 radical obtained by two methods: from SIN-1 and from a simple redox reaction. These reactions were investigated using the stopped-flow technique. The measurements were carried out at temperatures ranging from 5 to 25 degrees C over a pH range from 6.52 to 9.11 for cis-[Cr(C2O4)(Hpm) (OH2)2]+ and from 6.03 to 8.15 for cis-[Cr(C2O4)(hm)(OH2)2] +. We also determined the thermodynamic activation parameter (E(a)) and the uptake mechanism for each of the coordination compounds studied.

Chromium↗
PubMed1998

Utilization of DNA-protein cross-links as a biomarker of chromium exposure.

Human exposure to carcinogenic Cr(VI) compounds is found among workers in a large number of professional groups, and it can also occur through environmental pollution. A significant number of toxic waste sites contain Cr as a major contaminant. In this paper we summarize our efforts to apply measurements of DNA-protein cross-links (DPC) as test for biologically active doses of Cr(VI). DPC were found at elevated levels in lymphocytes in several human populations with low to medium Cr exposures. At high exposure to Cr(VI), exemplified by a group of Bulgarian chromeplaters, DPC plateaued and adducts' levels were similar to those found in environmentally exposed individuals. Lymphocytic DPC correlated strongly with Cr levels in erythrocytes that are indicative of Cr(VI) exposure. DPC in lymphocytes were not confounded by such variables as smoking, age, body weight, gender, or ethnicity. A new version of the cross-link assay offers improved sensitivity and requires a small amount of biologic material. Preliminary results indicate that the ability of DPC to reach detectable levels at low levels of Cr exposure could be related to a lack of repair of these lesions in lymphoid cells. Cr(III)-mediated cross-links of DNA with peptide glutathione or single amino acids were mutagenic in human cells, with a relationship of higher molecular weight of the peptide/amino acid correlating with a more potent mutagenic response. We speculate that bulky DPC could also have a significant promutagenic effect. The current methodology does not allow specific determination of Cr-induced DPC; however, demonstrated sensitivity of DPC measurements and the assay's large sample capacity may allow this assay to be used as the initial screening test for the occurrence of DNA damage in Cr(VI)-exposed populations.

Biomarkers↗
PubMed2005

Effect of texture of polishing particle on the surface roughness of a cobalt-chromium alloy using a centrifugal shooting type polishing machine.

In a previous report, we investigated the influence of the shooting angle of polishing particle on the surface roughness of a cobalt-chromium (Co-Cr) alloy using a centrifugal shooting type polishing machine. In the present work, we examined the effects of the texture of polishing particle and polishing time on the surface roughness of Co-Cr alloy cast specimens. Nine different textures of polishing particle were investigated with respect to core material and particle abrasiveness: three different elastic body cores (core A, hard chloroprene rubber; core B, soft chloroprene rubber; core C, natural rubber) and three different green carborundum powders as abrasives (#800, #3000, and #6000). Polishing was performed under a fixed shooting angle of 30 degrees for six different polishing times (1, 2, 3, 5, 7, and 10 minutes). Surface roughness (Ra, Sm) and cutting depth on the polished surface were measured after each polishing stage. Surface roughness was significantly improved within three minutes, particularly using a polishing particle with rough carborundum powder (#800 or #3000) and a heavy core (core A or core B). Cutting depth increased in proportion to polishing time and roughness of carborundum powder, and was least with core C. These results suggested that a polishing particle composed of core B and #3000 carborundum paste was superior for the intermediate polishing of a Co-Cr alloy, and that polishing time should be limited to within three minutes.

Analysis of Variance↗
PubMed2004

Aqua(2,2'-diamino-4,4'-bi-1,3-thiazole-kappa2N,N')(iminodiacetato-kappa3O,N,O')chromium(III) chloride monohydrate.

Crystals of the title compound, [Cr(C4H5NO4)(C6H6N4S2)(H2O)]Cl.H2O, consist of Cr(III) complex cations, Cl- counter-ions and lattice water molecules. The complex cation assumes an octahedral coordination geometry, formed by a tridentate iminodiacetate dianion (IDA), a diaminobithiazole (DABT) molecule and a water molecule. The planar DABT group chelates the Cr(III) ion with normal Cr-N distances [2.0574 (17) and 2.0598 (17) A], but the DABT molecule is inclined to the coordination plane by a dihedral angle of 17.23 (7) degrees. In the monodentate carboxylate groups of the IDA ion, the coordinated C-O bonds [1.288 (3) and 1.284 (3) A] are much longer than the uncoordinated C-O bonds [1.222 (3) and 1.225 (3) A].

Journal Article↗
PubMed2000

Flame atomic absorption spectrometric determination of trace chromium in various standard samples after preconcentration with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol.

Chromium can be quantitatively retained as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)-tetra-phenylborate(TPB) complex onto microcrystalline naphthalene in the pH range 4.8-5.9 from a large volume of aqueous solutions of various standard samples. After filtration, the solid mass consisting of the chromium complex and naphthalene was dissolved with 5 mL of dimethylformamide and the metal was determined by air-acetylene FAAS. A detection limit of 4 ng/mL for chromium was established. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of chromium in various standard alloys and biological samples.

Anions↗